Semiconductor package

ABSTRACT

The present invention relates to a semiconductor package. The semiconductor package includes a substrate, at least one chip, a plurality of conductive elements, a plurality of first conductors and a molding compound. The substrate has a plurality of first pads and a solder mask. The first pads are exposed to a first surface of the substrate, and the material of the first pads is copper. The solder mask is disposed on the first surface, contacts the first pads directly, and has at least on opening so as to expose part of the first pads. The chip is mounted on the first surface of the substrate. The conductive elements electrically connect the chip and the substrate. The first conductors are disposed on the first pads. The molding compound is disposed on the first surface of the substrate, and encapsulates the chip, the conductive elements and part of the first conductors. Whereby, the solder mask contacts the first pads directly, and thus results in higher bonding strength, so as to avoid the bridge between the first conductors caused by the first conductors permeating into the interface between the solder mask and the first pads.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. application Ser. No. 12/818,422 filed Jun. 18, 2010, which claims the benefit of Taiwan Application Serial No. 098146112 filed Dec. 31, 2009, the disclosures of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor package, and more particularly to a semiconductor package which can avoid solder bridge.

2. Description of the Related Art

FIGS. 1 to 4 show schematic views of a method for making a conventional semiconductor package. As shown in FIG. 1, a substrate 11 is provided. The substrate 11 has a first surface 111, a second surface 112, a plurality of first pads 113, a plurality of second pads 114, a Ni/Au plating layer 115 and a solder mask 116. The first pads 113 are exposed to the first surface 111. The second pads 114 are exposed to the second surface 112. The Ni/Au plating layer 115 is formed on the entire upper surface of the first pad 113. The solder mask 116 contacts the Ni/Au plating layer 115 directly, and has at least one opening so as to expose part of the Ni/Au plating layers 115. Then, a chip 12 is mounted on the substrate 11, and a plurality of conductive elements (for example, a plurality of wires 13) are formed so as to electrically connect the chip 12 and the first surface 111 of the substrate 11. Then, a plurality of first conductors (for example, a plurality of first solder balls 14) are formed on the Ni/Au plating layer 115.

As shown in FIG. 2, a molding compound 15 is formed on the first surface 111 of the substrate 11, so as to encapsulate the chip 12, the wires 13 and the first solder balls 14. As shown in FIG. 3, a plurality of second solder balls 16 are formed on the second pads 114, and the second solder balls 16 are reflowed. As shown in FIG. 4, part of a periphery area of the molding compound 15 is removed, so that the molding compound 15 has at least two heights, and one end of the first solder balls 14 is exposed. Thus, the conventional semiconductor package 1 is formed.

The conventional semiconductor package 1 has the following disadvantages. First, the solder mask 116 contacts the Ni/Au plating layer 115 directly, however the solder mask 116 and the Ni/Au plating layer 115 has low bonding strength, therefore delamination between the solder mask 116 and the Ni/Au plating layer 115 occurs easily. Moreover, the Ni/Au plating layer 115 disposed on the first solder balls 14 is encapsulated by the molding compound 15, and when the second solder balls 16 are reflowed, the first solder balls 14 expand because of high temperature. Meanwhile, the first solder balls 14 extrude to adjacent elements and protrude to the interface between the solder mask 116 and the Ni/Au plating layer 115 which has low bonding strength. As a result, it leads to the bridge between the first solder balls 14, as shown in area A of FIGS. 3 to 5, and the yield rate of the semiconductor package is decreased.

Therefore, it is necessary to provide a semiconductor package to solve the above problems.

SUMMARY OF THE INVENTION

The present invention is directed to a semiconductor package. The semiconductor package comprises a substrate, at least one chip, a plurality of conductive elements, a plurality of first conductors and a molding compound. The substrate has a first surface, a second surface, a plurality of first pads and a solder mask. The first pads are exposed to the first surface, and the material of the first pads is copper. The solder mask directly contacts the first pads, and has at least one opening so as to expose part of the first pads. The chip is mounted on the substrate. The conductive elements electrically connect the chip and the substrate. The first conductors are disposed on the first pads. The molding compound is disposed on the first surface of the substrate, and encapsulates the chip, the conductive elements and the first conductors. The molding compound has a first top surface and a second top surface. The horizontal level of the first top surface is different from that of the second top surface, and one end of the first conductors is exposed. A top surface of the exposed first conductors is level with the second top surface of the molding compound.

The present invention is further directed to a semiconductor package. The semiconductor package comprises a substrate, at least one chip, a plurality of conductive elements, a plurality of first conductors and a molding compound. The substrate has a first surface, a second surface, a plurality of first pads and a solder mask. The first pads are exposed to the first surface, and the material of the first pads is copper. The solder mask directly contacts the first pads, and has at least one opening so as to expose part of the first pads. The chip is mounted on the substrate. The conductive elements electrically connect the chip and the substrate. The first conductors are disposed on the first pads. The molding compound is disposed on the first surface of the substrate, and encapsulates the chip, the conductive elements and part of the first conductors. The molding compound has a first surface and a plurality of blind holes. The blind holes open at the first surface of the molding compound, and expose part of the first conductors.

Whereby, the solder mask contacts the first pads directly, and thus results in higher bonding strength, so as to avoid the bridge between the first conductors caused by the first conductors permeating into the interface between the solder mask and the first pads.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 are schematic views of a method for making a conventional semiconductor package;

FIG. 5 is a partially enlarged photograph of FIG. 4;

FIG. 6 is a cross-sectional view of a semiconductor package according to a first embodiment of the present invention; and

FIG. 7 is a cross-sectional view of a semiconductor package according to a second embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 6 shows a cross-sectional view of a semiconductor package according to a first embodiment of the present invention. The semiconductor package 2 comprises a substrate 21, at least one chip 22, a plurality of conductive elements (for example, a plurality of wires 23), a plurality of first conductors (for example, a plurality of first solder balls 24), a molding compound 25 and a plurality of second solder balls 26. The substrate 21 has a first surface 211, a second surface 212, a plurality of first pads 213, a plurality of second pads 214, a solder mask 216 and an anti-oxidation layer 217.

The first pads 213 are exposed to the first surface 211, and the material of the first pads 213 is copper. The second pads 214 are exposed to the second surface 212. The solder mask 216 contacts the first pads 213 directly, and has at least one opening so as to expose part of the first pads 213. The anti-oxidation layer 217 is disposed on the first pads 213 exposed to the opening of the solder mask 216. That is, the anti-oxidation layer 217 does not completely cover the entire upper surface of the first pad 213. In the embodiment, the anti-oxidation layer 217 is a Ni/Au plating layer. However, in other applications, the anti-oxidation layer 217 can be an organic solderability preservative (OSP), and the anti-oxidation layer 217 does not exist in the final structure. Therefore, the present invention can avoid the first pads 213 from oxidizing after being exposed in the air, and thus the yield rate of the semiconductor package is increased.

The chip 22 is mounted on the substrate 21. In the embodiment, the chip 22 is adhered to the solder mask 216. In the present invention, the form of the chip 22 has no limitation. The wires 23 electrically connect the chip 22 and the substrate 21. The first solder balls 24 are disposed on the first pads 213, preferably, the first solder balls 24 are hemispheres. The second solder balls 26 are disposed on the second pads 214.

The molding compound 25 is disposed on the first surface 211 of the substrate 21, and encapsulates the chip 22, the wires 23 and the first solder balls 24. The molding compound 25 has a first top surface 251 and a second top surface 252, the horizontal level of the first top surface 251 is different from that of the second top surface 252, and one end of the first solder balls 24 is exposed. A top surface of the exposed first solder balls 24 is level with the second top surface 252 of the molding compound 25.

The molding compound 25 has a first height H₁ and a second height H₂, the first height H₁ is the height from the first top surface 251 to the solder mask 216, the second height H₂ is the height from the second top surface 252 to the solder mask 216, and the first height H₁ is greater than the second height H₂.

FIG. 7 shows a cross-sectional view of a semiconductor package according to a second embodiment of the present invention. The semiconductor package 3 comprises a substrate 31, at least one chip 32, a plurality of conductive elements (for example, a plurality of wires 33), a plurality of first conductors (for example, a plurality of first solder balls 34), a molding compound 35 and a plurality of second solder balls 36. The substrate 31 has a first surface 311, a second surface 312, a plurality of first pads 313, a plurality of second pads 314, a solder mask 316 and an anti-oxidation layer 317.

The first pads 313 are exposed to the first surface 311, and the material of the first pads 313 is copper. The second pads 314 are exposed to the second surface 312. The solder mask 316 contacts the first pads 313 directly, and has at least one opening so as to expose part of the first pads 313. The anti-oxidation layer 317 is disposed on the first pads 313 exposed to the opening of the solder mask 316, preferably, the anti-oxidation layer 317 is an organic solderability preservative (OSP) or a Ni/Au plating layer. Therefore, the present invention can avoid the first pads 313 from oxidizing after being exposed in the air, and thus the yield rate of the semiconductor package is increased.

The chip 32 is mounted on the substrate 31. In the embodiment, the chip 32 is adhered to the solder mask 316. In the present invention, the form of the chip 32 has no limitation. The wires 33 electrically connect the chip 32 and the substrate 31. The first solder balls 34 are disposed on the first pads 313. The second solder balls 36 are disposed on the second pads 314. The molding compound 35 is disposed on the first surface 311 of the substrate 31, and encapsulates the chip 32, the wires 33 and part of the first solder balls 34. The molding compound 35 has a first surface 351 and a plurality of blind holes 352. The blind holes 352 open at the first surface 351 of the molding compound 35, and expose part of the first solder balls 34.

Therefore, the solder masks 216, 316 contact the first pads 213, 313 directly, and thus results in higher bonding strength, so as to avoid the bridge between the first conductors (the first solder balls 24, 34) caused by the first conductors (the first solder balls 24, 34) permeating into the interface between the solder masks 216, 316 and the first pads 213, 313.

While several embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention should not be limited to the particular forms as illustrated, and that all modifications which maintain the spirit and scope of the present invention are within the scope defined by the appended claims. 

What is claimed is:
 1. A semiconductor package, comprising: a substrate comprising a top surface, a pad, an anti-oxidation layer, and a solder mask, wherein the pad is disposed adjacent to the top surface of the substrate, the solder mask overlies and directly contacts a part of the pad and defines a solder mask opening so as to expose a remaining part of the pad, and the anti-oxidation layer is disposed over the remaining part of the pad exposed by the solder mask opening; a chip mounted on the substrate; a plurality of conductive elements electrically connecting the chip and the substrate; a conductor disposed over the anti-oxidation layer; and a molding compound disposed over the top surface of the substrate, wherein the molding compound comprises a first top surface and a second top surface, a first height of the first top surface of the molding compound is different from a second height of the second top surface of the molding compound, and a top end of the conductor is exposed adjacent to the second top surface of the molding compound.
 2. The semiconductor package of claim 1, wherein the anti-oxidation layer is a plating layer.
 3. The semiconductor package of claim 2, wherein a width of the plating layer is smaller than a width of the pad.
 4. The semiconductor package of claim 1, wherein the conductor is a solder ball having a hemispherical shape.
 5. The semiconductor package of claim 1, wherein the first top surface of the molding compound overlies the chip and the conductive elements, and the first height is greater than the second height.
 6. The semiconductor package of claim 1, wherein the top end of the conductor is substantially coplanar with the second top surface of the molding compound.
 7. The semiconductor package of claim 1, wherein the pad comprises copper.
 8. A semiconductor package, comprising: a substrate comprising a top surface, a pad, and a solder mask, wherein the pad is disposed adjacent to the top surface of the substrate, and the solder mask defines a solder mask opening that partially exposes the pad to define a covered portion and an uncovered portion of the pad; a conductor disposed over the uncovered portion of the pad; and a molding compound disposed over the top surface of the substrate, wherein the molding compound comprises a first top surface and a second top surface, the second top surface of the molding compound is recessed below the first top surface of the molding compound, and a top end of the conductor is exposed adjacent to the second top surface of the molding compound.
 9. The semiconductor package of claim 8, wherein the solder mask directly contacts the covered portion of the pad.
 10. The semiconductor package of claim 8, wherein the covered portion of the pad is adjacent to a periphery of the pad.
 11. The semiconductor package of claim 8, wherein the substrate further comprises an anti-oxidation layer disposed over the uncovered portion of the pad.
 12. The semiconductor package of claim 11, wherein the anti-oxidation layer is inwardly recessed from a periphery of the pad.
 13. The semiconductor package of claim 11, wherein a top surface of the anti-oxidation layer is recessed below a top surface of the solder mask.
 14. The semiconductor package of claim 8, wherein a width of the solder mask opening at a top surface of the solder mask is substantially the same as a width of the solder mask opening adjacent to the pad.
 15. A semiconductor package, comprising: a substrate comprising a top surface, a pad, and an anti-oxidation layer, wherein the pad is disposed adjacent to the top surface of the substrate, and the anti-oxidation layer is disposed over a central part of the pad while a peripheral part of the pad is exposed by the anti-oxidation layer; a chip disposed over the top surface of the substrate; a conductor disposed over the anti-oxidation layer; and a molding compound disposed over the top surface of the substrate, wherein the molding compound comprises a first top surface and a second top surface, the second top surface of the molding compound is recessed below the first top surface of the molding compound, and a top end of the conductor is exposed adjacent to the second top surface of the molding compound.
 16. The semiconductor package of claim 15, wherein the substrate further comprises a solder mask disposed adjacent to the top surface of the substrate, and the solder mask directly contacts the peripheral part of the pad.
 17. The semiconductor package of claim 16, wherein the solder mask defines a solder mask opening that exposes the anti-oxidation layer.
 18. The semiconductor package of claim 16, wherein a top surface of the anti-oxidation layer is recessed below a top surface of the solder mask.
 19. The semiconductor package of claim 15, wherein the anti-oxidation layer is a plating layer that comprises at least one of gold and nickel.
 20. The semiconductor package of claim 15, wherein the top end of the conductor is substantially coplanar with the second top surface of the molding compound. 